Photobioreactor systems and methods

ABSTRACT

An algal growth system can include a frame and a flexible sheet material that can have a substantially vertical orientation, where the flexible sheet material can facilitate the growth and attachment of algae, where the flexible sheet material can be supported by the frame.

REFERENCE TO RELATED APPLICATIONS

The present application claims the priority benefit of U.S. provisionalpatent application Ser. No. 61/783,737, filed Mar. 14, 2013, and herebyincorporates the same application herein by reference in its entirety.

TECHNICAL FIELD

Embodiments of the technology relate, in general, to biofilm technology,and in particular to a revolving algal biofilm (RAB) photobioreactor forstimulating algal growth and simplified biomass harvesting.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be more readily understood from a detaileddescription of some example embodiments taken in conjunction with thefollowing figures:

FIG. 1 depicts a flow chart illustrating the methodology generallyassociated with algae harvesting.

FIG. 2 depicts a top view of microalgae being grown on polystyrene foam.

FIG. 3 depicts a partial cutaway perspective view of a revolving algalbiofilm photobioreactor according to one embodiment.

FIG. 4 depicts a schematic front view of the revolving algal biofilmphotobioreactor illustrated in FIG. 3.

FIG. 5 depicts a top view of microalgae being grown on a variety ofmaterials.

FIG. 6 depicts a bar chart of harvesting frequencies for an algal strainaccording to one embodiment.

FIG. 7 depicts a partial cutaway perspective view of the revolving algalbiofilm bioreactor illustrated in FIG. 3, shown with grow lights and agas input.

FIG. 8 depicts a partial exploded view of the revolving algal biofilmbioreactor shown in FIG. 3.

FIG. 9 depicts a perspective view of a revolving algal biofilmbioreactor having a plurality of associated algal growth systems and araceway according to one embodiment.

FIG. 10 depicts a perspective view of the algal growth systemillustrated in FIG. 12.

FIG. 11 depicts a perspective view of the raceway illustrated in FIG.12.

FIG. 12 depicts a perspective view of a revolving algal biofilmbioreactor having a plurality of associated algal growth systems and araceway according to an alternate embodiment.

FIG. 13 depicts a perspective view of the algal growth systemillustrated in FIG. 12.

FIG. 14 depicts a perspective view of a revolving algal biofilmbioreactor having an associated algal growth system and a trough systemaccording to one embodiment.

FIG. 15 depicts a perspective view of the algal growth systemillustrated in FIG. 14.

FIG. 16 depicts a perspective view of the trough system illustrated inFIG. 14.

FIG. 17 depicts a perspective view of an algal growth system shown witha harvesting system according to one embodiment.

FIG. 18 depicts a perspective view of an algal growth system accordingto one embodiment.

FIG. 19 depicts a perspective view of a photobioreactor according to oneembodiment.

FIG. 20 depicts a flow chart showing a method for growing and harvestingalgae using a raceway according to one embodiment.

FIG. 21 depicts a flow chart showing a method for growing and harvestingalgae using a trough according to one embodiment.

SUMMARY

An algal growth system can include a frame and a flexible sheet materialthat can have a substantially vertical orientation, where the flexiblesheet material can be configured to facilitate the growth and attachmentof algae, where the flexible sheet material can be supported by theframe. The algal growth system can include a first drive shaft, wherethe first drive shaft can be coupled with the frame, where the firstdrive shaft can support and actuate the flexible sheet material, a gearsystem, where the gear system can be coupled with the first drive shaft,a first roller, where the first roller can be coupled with the frame andcan be configured to guide the flexible sheet material, and a drivemotor, where the drive motor can be coupled with the gear system, wherethe drive motor can actuate the gear system and the at least one driveshaft such that the flexible sheet material can be actuated.

A method of growing algae can include the step of providing an algalgrowth system that can include a frame and a flexible sheet materialthat can have a substantially vertical orientation, where the flexiblesheet material can be configured to facilitate the growth and attachmentof algae, where the flexible sheet material can be supported by theframe. The algal growth system can include a first drive shaft, wherethe first drive shaft can be coupled with the frame, where the firstdrive shaft can support and actuate the flexible sheet material, a gearsystem, where the gear system can be coupled with the first drive shaft,a first roller, where the first roller can be coupled with the frame andcan be configured to guide the flexible sheet material, and a drivemotor, where the drive motor can be coupled with the gear system, wherethe drive motor can actuate the gear system and the at least one driveshaft such that the flexible sheet material can be actuated. The methodfor growing algae can include the steps of providing a liquid reservoircontaining a contacting liquid, rotating the flexible sheet material ofthe algal growth system through a liquid phase, rotating the flexiblesheet material of the algal growth system through a gaseous phase, andharvesting the algae from the flexible sheet material.

DETAILED DESCRIPTION

Various non-limiting embodiments of the present disclosure will now bedescribed to provide an overall understanding of the principles of thestructure, function, and use of the proficiency tracking systems andprocesses disclosed herein. One or more examples of these non-limitingembodiments are illustrated in the accompanying drawings. Those ofordinary skill in the art will understand that systems and methodsspecifically described herein and illustrated in the accompanyingdrawings are non-limiting embodiments. The features illustrated ordescribed in connection with one non-limiting embodiment may be combinedwith the features of other non-limiting embodiments. Such modificationsand variations are intended to be included within the scope of thepresent disclosure.

Reference throughout the specification to “various embodiments,” “someembodiments,” “one embodiment,” “some example embodiments,” “one exampleembodiment,” or “an embodiment” means that a particular feature,structure, or characteristic described in connection with any embodimentis included in at least one embodiment. Thus, appearances of the phrases“in various embodiments,” “in some embodiments,” “in one embodiment,”“some example embodiments,” “one example embodiment,” or “in anembodiment” in places throughout the specification are not necessarilyall referring to the same embodiment. Furthermore, the particularfeatures, structures or characteristics may be combined in any suitablemanner in one or more embodiments.

Traditionally, algae are grown in open raceway ponds or enclosedphotobioreactors, where algae cells are in suspension and are harvestedthrough sedimentation, filtration, or centrifugation. Due to the lightpenetration problem caused by mutual shading of suspended algal cells,the algal growth in suspension is often limited by light availability.Also, due to the small size (3-30 μm) of algae cells and the dilutealgae concentration (<1% w/v), gravity sedimentation of suspended cellsoften takes a long time in a large footprint settling pond. Filtrationof algal cells from the culture broth can result in filter fouling.Centrifugation can achieve high harvest efficiency; however, the capitalinvestment and operational cost for a centrifugation system can beprohibitively expensive. Due to these drawbacks, an alternative methodfor growing and harvesting algae biomass may be advantageous.

Described herein are example embodiments of revolving algal biofilmphotobioreactor systems and methods that can enhance cell growth andsimplify biomass harvesting. In one example embodiment, systems andmethods can provide cost effective harvesting of algae biomass. In someembodiments, systems and methods can be used to produce algae forbiofuel feedstock, and aquacultural feed, and nutraceuticals. In someembodiments, algal cells can be attached to a material that can berotated between a nutrient-rich liquid phase and a carbon dioxide richgaseous phase such that alternative absorption of nutrients and carbondioxide can occur. The algal cells can be harvested by scraping from thesurface to which they are attached, which can eliminate harvestprocedures commonly used in suspension cultivation systems, such assedimentation, flocculation, floatation, and/or centrifugation. It willbe appreciated that systems and methods described herein can be combinedwith sedimentation, centrifugation, or any other suitable processes.

The examples discussed herein are examples only and are provided toassist in the explanation of the apparatuses, devices, systems andmethods described herein. None of the features or components shown inthe drawings or discussed below should be taken as mandatory for anyspecific implementation of any of the apparatuses, devices, systems ormethods unless specifically designated as mandatory. For ease of readingand clarity, certain components, modules, or methods may be describedsolely in connection with a specific figure. Any failure to specificallydescribe a combination or sub-combination of components should not beunderstood as an indication that any combination or sub-combination isnot possible. Also, for any methods described, regardless of whether themethod is described in conjunction with a flow diagram, it should beunderstood that unless otherwise specified or required by context, anyexplicit or implicit ordering of steps performed in the execution of amethod does not imply that those steps must be performed in the orderpresented but instead may be performed in a different order or inparallel.

Example embodiments described herein can mitigate air and waterpollution while delivering high value bio-based products such asbio-fuels, nutraceuticals, and animal feeds from microalgae. Exampleembodiments of RAB technology can play a beneficial role in creating analgal culture system that can economically produce algae biomass for,for example, biofuels, nutraceuticals, and animal feeds. Microalgae mayhave a significant impact in the renewable transportation fuels sector.Example embodiments can grow microalgae that can be used in biofuelproduction with a low harvest cost. Algae, if produced economically, mayalso serve as a primary feed source for nutraceuticals and aqua feedsproduction.

Example systems and methods can include developing a biofilm-basedmicroalgae cultivation system (RAB) that could be widely adapted by themicroalgae industry for producing, for example, fuels and high valueproducts, as well as for treating municipal, industrial, andagricultural wastewater. Microalgae use photosynthesis to transformcarbon dioxide and sunlight into energy. This energy is stored in thecell as oil, which has a high energy content. The oil yield from algaecan be significantly higher than that from other oil crops. Algae oilcan generally be easily converted to biodiesel and could replacetraditional petroleum-based diesel. In addition to fuel production,microalgae have also been rigorously researched for the potential toproduce various high value products such as animal feed, omega-3polyunsaturated fatty acids, pigments, and glycoproteins.

Referring to FIG. 1, low biomass productivity and high cost of algaeproduction can still be the major limitation in industrial scaleoperation. Example embodiments described herein may minimize such costsassociated with the growth and harvesting of algal cells from an aqueousculture system.

Generally, research on algae cultivation is done using suspended algaeculture. This culture method can have drawbacks including low biomassyield and productivity and low efficiency of harvesting the algal cellsfrom liquid culture medium. Example embodiments described herein canpromote a fast cell growth and a simple economical harvesting methodthat may be an improvement over existing methods. Example embodimentscan include an algal growth system or mechanized harvesting system,which can remove concentrated algae in-situ from an attachment materialand can minimize the amount of de-watering needed post-harvest. Exampleembodiments can optimize gas mass transfer due to the algae cells comingin direct contact with gaseous carbon dioxide when the algae are rotatedthrough the open air. In an alternate embodiment, the algae can berotated within an enclosed greenhouse 40 (FIGS. 3 and 4) having anincreased carbon dioxide concentration relative to the atmosphere, whichmay improve the growth rate of the algae. Example embodiments canutilize minimal growth medium, where the triangular or vertical designin example embodiments may reduce the total water needed for the growthand the chemical costs of growth medium. In one embodiment, suchadvantages may be accomplished by submerging only the lowest portion ofa bioreactor, supporting material, algal growth system, or mechanizedharvesting system into the medium.

Referring to FIG. 2, microalgae can be grown on the surface ofpolystyrene foam. FIG. 2 illustrates how algae can be harvested byscraping the surface of the foam. The mechanical separation throughscraping of biomass from the attached materials can result in biomasswith water content similar to centrifuged samples (e.g., 80-95% watercontent) and the residual biomass left on the surface can serve as anideal inoculum for subsequent growth cycles.

Referring to FIGS. 3, 4, 7, and 8, an example embodiment of a revolvingalgal biofilm photobioreactor (RAB) 10, in which algal cells 18 can beattached to a solid surface of a supporting material 12, is disclosed.The photobioreactor 10 can keep the algal cells 18 fixed in one placeand can bring nutrients to the cells, rather than suspend the algae in aculture medium. As shown in FIGS. 3 and 4, algal cells can be attachedto the supporting material 12 that is rotating between a nutrient-richliquid phase 15 and a CO2-rich gaseous phase 16 for alternativeabsorption of nutrients and carbon dioxide. The algal biomass can beharvested by scrapping the biomass from the attached surface with aharvesting squeegee 20 (FIG. 4) or other suitable device or system. Inexample embodiments, the naturally concentrated biofilm can be in-situharvested during the culture process, rather than using an additionalsedimentation or flocculation step for harvesting, for example. Theculture can enhance the mass transfer by directly contacting algal cellswith CO2 molecules in gaseous phase, where traditional suspended culturesystems may have to rely on the diffusion of CO2 molecules from gaseousphase to the liquid phase, which may be limited by low gas-liquid masstransfer rate. Example embodiments may only need a small amount of waterby submerging the bottom of the triangle-shaped algal growth system ormechanized harvesting system 22 in contacting liquid 14 while maximizingsurface area for algae to attach. Example embodiments can be scaled upto an industrial scale because the system may have a simple structureand can be retrofit on existing raceway pond systems. Exampleembodiments can be used in fresh water systems and can be adapted tosaltwater culture systems. For example, embodiments of this system canbe placed in the open ocean instead of in a raceway pond reactor. Inthis example application, the ocean can naturally supply the algae withsufficient sunlight, nutrient, water, and CO2, which in turn maydecrease operational costs. Referring to FIG. 7, a gas input 43 and growlights 42 having any suitable wavelength can be provided in the system.

Still referring to FIGS. 3, 4, 7, and 8, embodiments of the system caninclude a drive motor 24 and a gear system 26 that can rotate one or aplurality of drive shafts 28, where the one or a plurality of driveshafts 28 can correspondingly rotate the supporting material 12, such asa flexible sheet material. The supporting material 12 can be rotatedinto contact with the contacting liquid 14, which can allow the algalcells 18 to attach to the supporting material 12. The drive motor 24 caninclude a gear system 26 or pulley system that can drive the one or aplurality of drive shafts 28, where the one or a plurality of driveshafts 28 can rotate the supporting material 12 in and out of acontacting liquid 14, for example. Embodiments can also include a liquidreservoir 30, mister, water dripper, or any other suitable component ormechanism that can keep algae, which can be attached to the supportmaterial 12, moist. Embodiments can include any suitable scrapingsystem, vacuum system or mechanism for harvesting the algal cells 18from the supporting material 12. It will be appreciated that the systemcan include one or a plurality of rollers (not shown) that can be guideand support the supporting material 112 in addition to the one or aplurality of drive shafts 28.

In an example embodiment, a generally triangle-shaped mechanizedharvesting system 22 can be provided. Such a configuration can bebeneficial in maximizing the amount of sunlight or light that algalcells 18 are exposed to. However versions of the system can be designed,for example, in any configuration that includes a “sunlight capture”part 32 which can be exposed to air and sunlight, and a “nutrientcapture” part 34 which can be submerged into a nutrient solution orcontacting liquid 14. It will be appreciated that, in a first position,the supporting material 12 can have a portion that is in the “sunlightcapture” part 32 and a portion that is in the “nutrient capture” part34, where rotation of the supporting material 12 to a second positioncan result in different regions corresponding to the “sunlight capture”part 32 and “nutrient capture” part 34. Such movement of the supportingmaterial 12 can, for example, beneficially transition algal cells 18from a nutrient rich liquid to a region with sunlight and a carbondioxide content higher than the outside atmosphere. As will be shown inmore detail herein, a substantially vertical design is contemplated,which may be the simplest and most cost efficient design because such asystem may minimize the amount of wasted space and may maximize theamount of algae produced in a small area by growing this systemvertically. Alternative designs can include a straight vertical reactor,a reactor that is straight but slightly angled to provide more surfacearea for sunlight to hit, a cylindrical reactor, or a square shapedreactor.

Referring to FIG. 8, the generally triangle-shaped algal growth andmechanized harvesting system 22 can include a supporting material 12that is movable or removable relative to the liquid reservoir 30. Thesupporting material 12, and any associated components such as the one ora plurality of drive shafts 28 and gear system 26, can be movable orremovable for cleaning, replacement, harvesting, adjustment, or thelike. It will be appreciated that such movement can be manual or can beautomated if desirable. In an example embodiment, the liquid reservoir30 can contain a contacting liquid 14 having a first chemical or fluidmakeup, where the supporting material 12 can be lifted or otherwisetransitioned from the liquid reservoir 30 into a second liquid reservoir(not shown) having a second liquid (not shown) having a differentchemical or fluid makeup from the contacting liquid 14. In this manner,the supporting material 12 retaining algal cells 18 can be dipped ortransitioned into a variety of fluids or materials that may maximizealgal growth or otherwise provide a benefit. Such a system can berepeated or adjusted as appropriate. In an alternate embodiment, thesupporting material can be lifted or moved from the liquid reservoir 30and transitioned to a harvesting station. In one embodiment, harvestingcan take place while the supporting material 12 is positioned within theliquid reservoir 30.

Still referring to FIG. 8, the liquid reservoir 30 can include a pump 38or any other suitable actuator or fluid control. The pump 38 cancirculate the contacting liquid 14, which may improve the growth ofalgal cells 18 and the efficiency of the overall system. It will beappreciated that the pump 38 can be an electric pump, a wheel, apaddlewheel, or can have any other suitable configuration to create anydesirable flow pattern. It will be appreciated that the pump 38 canheat, cool, or otherwise adjust the conditions associated with thecontacting liquid 14. The pump 38 can also be configured for thedelivery of supplemental nutrients, such as supplemental fluidsdelivered at pre-specified times, where such delivery can be manual orautomated. It will be appreciated that the pump 38, and any othersuitable components, can be associated with a computer, controller, ormicrocontroller that can be programmed to provide any suitable automatedfunctionality.

Referring to FIG. 5, any suitable supporting material 12, such as anysuitable flexible fabric, can be used with the systems and methodsdescribed herein to grow any suitable material. For example, themicroalga Chlorella, such as Chlorella vulgaris can be grown onmaterials such as, muslin cheesecloth, aramid fiberglass, porous PTFEcoated fiberglass, chamois, vermiculite, microfiber, synthetic chamois,fiberglass, burlap, cotton duct, velvet, TYVEK, poly-lactic acid,abrased poly-lactic acid, vinyl laminated nylon, polyester, wool,acrylic, lanolin, woolen, cashmere, leather, silk, lyocell, hemp fabric,SPANDEX, polyurethane, olefin fiber, polylactide, LUREX, carbon fiber,and combinations thereof. The supporting material or associated materialcan include rubbers such as, for example, buna-n Rubber, butyl rubber,ECH rubber, EPDM rubber, gum rubber, polyethylene rubber, latex rubber,neoprene rubber, polyurethane, santoprene rubber, SBR rubber, siliconerubber, vinyl rubber, VITON fluoroelastomer, aflas, fuorosilicone, orcombinations thereof. The supporting material or associated material caninclude plastics such as, for example, PETG, acrylic, cast acrylic,cellulose, polycarbonate, LDPE, PLA, PVC, ABS, polystyrene, HDPE,polypropylene, UHMW, delrin, acetal resin, nylon, cast nylon, CPVC,rexolite polystyrene, noryl PPO, polyester, PVDF, polysulfone, radelPPSU, ulrem PEI, FEP, PPS, PEEK, PFA, torlon PAI, reflon PTFE,polyimide, antistatic polycarbonate, antistatic cast acrylic, conductiveABS/PVC, antistatic acetal, atatic-dissipative UHMW, conductive UHMW,antistatic PTFE, glass-filled polycarbonate, strengthened acrylic,strengthened PVC, glass-filled nylon, glass-Filled acetal, glass-filledUHMW, glass-filled PTFE, and combinations thereof. The supportingmaterial and associated materials can include metals such as, forexample, aluminum, steel, cast iron, tungsten carbide, tungsten alloy,stainless steel, nickel, titanium, copper, brass, bronze, lead, tin,zinc, casting alloys, or combinations thereof. Any suitable material forthe supporting material and associated materials is contemplatedincluding ceramic, felt, fiberglass, foam, foam rubber, foam plastic,glass, leathers, carbon fiber, wire cloth, or the like.

The material associated with the supporting material 12 can have a highsurface roughness, high hydrophobicity, and high positive surface chargein one embodiment. It will be appreciated that any suitable texture,surface treatment, hybrid material, or the like is contemplated. Thesupporting material, belt, sheet, or band can be altered, modified, orchanged with heat, abrasion, applying another material, chemicallytreating, applying a charged molecule, applying a polar molecule, orcombinations thereof. Referring to FIG. 18, in one embodiment of analgal growth system 522, the supporting material 512 can including oneor a plurality of ribs 596, can be finned, or otherwise textured suchthat a pump is not needed to agitate an associated contacting liquid,where rotation of the textured supporting material can sufficientlyagitate or otherwise create a desirable fluid dynamic. The algal growthsystem 522 can also include an integrated paddle 598 that can bepositioned within a contacting liquid such that rotation of thesupporting material 512 correspondingly can rotate the integrated paddle598. In alternate embodiments, the supporting material can includeflexible regions and rigid regions, can be a hinged belt, can haveremovable sections, or can otherwise be suitably configured. Forexample, in one embodiment, strips of material can be attached to arotating belt with a hook and loop fastener, where such strips can bepulled off of the rotating belt during harvesting and replaced whenharvesting is complete.

The supporting material 12 can be reinforced by attaching a highstrength and slowly degradable second layer of material to a cell growthmaterial. The photobioreactor 10 can be configured such that the highstrength material comes in contact with components such as rollers,drive shafts, and the like. Such a configuration may help avoid thewearing off of the cell growth material during operation of thephotobioreactor 10. Suitable materials can include materials that arenot easily degraded by water and microbes such as plastic, rubber,TYVEK, or other slowly degrading materials. Additionally, materials,adhesives, chemicals, or the like can be sprayed onto or otherwiseprovided on the supporting material 12 to facilitate algal attachment.It will be appreciated that any suitable number of layers of material iscontemplated.

It will be appreciated that any suitable algal cells 18 (includingcyanobacteria) as well as fungal strains, such as strains that can beused in aquaculture feed, animal feed, nutraceuticals, or biofuelproduction can be used. Such strains can include Nannochloropsis sp.,which can be used for both biofuel production and aquacultural feed,Scenedesmus sp., a green microalga that can be used in wastewatertreatment as well as for fuel production feedstock, Haematococcus sp,which can produce a high level of astaxanthin, Botryococcus sp. a greenmicroalga with high oil content, Spirulina sp. a blue-green alga withhigh protein content, Dunaliella sp. a green microalga containing alarge amount of carotenoids, and/or a group of microalgae speciesproducing a high level of long chain polyunsaturated fatty acids caninclude Arthrospira, Porphyridium, Phaeodactylum, Nitzschia,Crypthecodinium and Schizochytrium. Any suitable parameter, includinggaseous phase CO2 concentration, harvesting frequency, the rotationspeed of the RAB reactor, the depth of the biofilm harvested, the ratioof submerged portion to the air-exposure portion of the RAB reactor, orthe gap between the different modules of the RAB system can be optimizedfor any suitable species. It will be appreciated that the listed genusand species are described by way of example and additions andcombinations are contemplated.

Referring to FIG. 6, any harvesting schedule can be used in accordancewith example embodiments described herein. The mechanism of harvestingbiomass from the biofilm can be, for example, scraping, high pressureair, vacuum, or combinations thereof. Biomass productivity may vary byspecies and any suitable harvesting time is contemplated to maximizesuch productivity. For example, as shown in FIG. 6, of this specificspecies as a function of harvesting time by growing the algae on a RABsystem then harvesting the cells at different durations. As shown inFIG. 6, for Chlorella the optimal harvest frequency may be every 7 days.In example embodiments, managing other parameters such as CO2concentration and nutrient loading may also impact algal growthperformance.

Referring to FIGS. 9-11, shown is an alternate embodiment of a revolvingalgal biofilm photobioreactor (RABP) 100, in which algal cells 118 canbe attached to a solid surface of a supporting material 112 that can berotated between a nutrient-rich liquid phase 115 and a CO2-rich gaseousphase 116 for alternative absorption of nutrients and carbon dioxide.The algal biomass can be harvested by scrapping the biomass from theattached surface with a harvesting mechanism (not shown) such as asqueegee, vacuum, reaper, or the like. The photobioreactor 100 mayrequire only a small amount of water for operation, relative to existingmethods, where only the bottom 150 (FIG. 10) of an algal growth unit ormechanized harvesting unit 122 may be immersed in a contacting liquid114. The photobioreactor 100 can include one or a plurality ofmechanized harvesting units 122, having frames 123, that can bepositioned in a raceway 130 containing contacting fluid 114. Exampleembodiments can include a large number of mechanized harvesting unitssuch that the photobioreactor can be scaled up to an industrial scale.For example, a single raceway could have 20, 50, 100, or more mechanizedharvesting units. In an example embodiment, the one or a plurality ofmechanized harvesting units 122 can be retrofitted onto existing racewaypond systems. Example embodiments can be used in fresh water systems andcan be also be adapted to saltwater culture systems. In one example, theocean can naturally supply the algal cells with sufficient sunlight,nutrient, water, and CO2, which in turn may decrease operational costsassociated with operation of a photobioreactor. Embodiments of themechanized harvesting units can be placed, for example, in any suitablefluid retaining location or device.

Embodiments of the photobioreactor 100 can include a drive motor 124 anda gear system 126 that can rotate one or a plurality of drive shafts128, where the one or a plurality of drive shafts 128 cancorrespondingly rotate the supporting material 112, such as a flexiblesheet material for growing algal cells 118. The photobioreactor 100 caninclude one or a plurality of rollers 129 that can support and guide thesupporting material 112. The supporting material 112 can be rotated intocontact with the contacting liquid 114, which can allow the algal cells118 to attach to the supporting material 112. The drive motor 124 caninclude a gear system 126 or pulley system that can drive the one or aplurality of drive shafts 128, where the one or a plurality of driveshafts 128 can rotate the supporting material 112 into and out of thecontacting liquid 114. Embodiments can also include a raceway 130,mister, water dripper, or any other suitable component or mechanism thatcan keep algae, which can be attached to the support material 112,moist. Embodiments can include any suitable scraping system, vacuumsystem or mechanism for harvesting the algal cells 118 from thesupporting material 112. It will be appreciated that the drive motor 124can be associated with a plurality of mechanized harvesting units 122or, in an alternate embodiment, each mechanized harvesting unit can beassociated with an independent motor, gear, and/or drive shaft system.It may be efficient to operate one or more of the mechanized harvestingunits on the same schedule, but it may also be advantageous to operatesome or all of the mechanized harvesting units on different schedules.For example, in one embodiment, a mechanized harvesting unit exposed tonatural light can be associated with a light sensor (not shown) andcontroller (not shown) such that the rotation speed of the supportingmaterial is optimized relative to the available light. In such anexample, mechanized harvesting units in the same facility may havedifferent, or slightly different environmental conditions, whereoperating each mechanized harvesting unit independently maysubstantially optimize the overall system.

The mechanized harvesting unit 122 can have a generally triangle-shapedconfiguration supported by the frame 123. It will be appreciated thatthe frame 123 can be constructed from any suitable material, such asmetal, and can have any suitable configuration. The frame 123 can besubstantially level relative to a flat surface, can be stepped, orotherwise shaped to accommodate an incline or an uneven surface. Theframe 123 can include telescoping components (not shown), such astelescoping legs, which may allow the frame to be used effectively as aretrofit in existing raceways, for example. The frame 123 can bestackable (not shown) or can be coupled in a side-by-side fashion withother frames in an interlocking manner such that a plurality ofmechanized harvesting systems can be connected to form aphotobioreactor. Such a modular system may allow for a few mechanizedharvesting system designs to be used in a wide variety of locations andsituations.

One or a plurality of mechanized harvesting units 122 can be associatedwith the raceway 130 in any suitable manner or configuration. Forexample, each mechanized harvesting unit 122 can be integral with orpermanently affixed to the raceway 130. In an alternate embodiment, eachmechanized harvesting unit 122 can be selectively removable oradjustable relative to the raceway 130, where the mechanized harvestingunit 122 can be removed for cleaning, harvesting, replacement, upgrade,or the like.

Referring to FIG. 11, the raceway 130 can have any suitable shape orconfiguration. In one example, the raceway 130 can include a motor 138that can be configured to drive a paddlewheel 139. The paddlewheel 139can be configured to create a current or flow within the raceway 130that may facilitate the growth of algal cells 118. It will beappreciated that the raceway, motor, and paddlewheel are shown by way ofexample only, where any suitable mechanism to provide a desirable flowor current in a suitable reservoir is contemplated. The raceway 130 canbe open or otherwise exposed to light such that algae can easily growwithin the raceway 130. The raceway 130 can have a region 141 that canbe exposed to light and may not contain a mechanized harvesting unit,where the region 141 can be used to cultivate or grow a supply of algalcells 118 within the raceway 130. Providing such a region 141, where theregion 141 can have any suitable shape or configuration, may make thesystem self-sustaining and may reduce the likelihood that the systemneeds to be seeded or re-seeded with algal cells.

Referring to FIGS. 12 and 13, shown is an alternate embodiment of arevolving algal biofilm photobioreactor (RAB) 200, in which algal cells218 can be attached to a solid surface of a supporting material 212 thatcan be rotated between a nutrient-rich liquid phase 215 and a CO2-richgaseous phase 216 for alternative absorption of nutrients and carbondioxide. The algal biomass can be harvested by scrapping the biomassfrom the attached surface with a harvesting mechanism (not shown) suchas a squeegee, vacuum, reaper, or the like. The photobioreactor 200 mayrequire only a small amount of water for operation, relative to existingmethods, where only the bottom 250 (FIG. 13) of an algal growth unit ormechanized harvesting unit 222 may be immersed in a contacting liquid214. The photobioreactor 200 can include one or a plurality ofmechanized harvesting units 222, having frames 223, which can bepositioned in a raceway 230 containing contacting fluid 214. Exampleembodiments can include a large number of mechanized harvesting unitssuch that the photobioreactor can be scaled up to an industrial scale.For example, a single raceway could have 20, 50, 100, or more mechanizedharvesting units. In an example embodiment, the one or a plurality ofmechanized harvesting units 222 can be retrofitted onto existing racewaypond systems. Embodiments of the mechanized harvesting units can beplaced, for example, in any suitable fluid retaining location or device.

Embodiments of the photobioreactor 200 can include a drive motor 224 anda gear system 226 that can rotate one or a plurality of drive shafts228, where the one or a plurality of drive shafts 228 cancorrespondingly rotate the supporting material 212, such as a flexiblesheet material for growing algal cells 218. The photobioreactor 200 caninclude one or a plurality of rollers 229 that can support and guide thesupporting material 112. The supporting material 212 can be rotated intocontact with the contacting liquid 214, which can allow the algal cells218 to attach to the supporting material 212. The drive motor 224 caninclude a gear system 226 or pulley system that can drive the one or aplurality of drive shafts 228, where the one or a plurality of driveshafts 228 can rotate the supporting material 212 into and out of thecontacting liquid 214. Embodiments can also include a raceway 230,mister, water dripper, or any other suitable component or mechanism thatcan keep algae, which can be attached to the support material 212,moist. Embodiments can include any suitable scraping system, vacuumsystem or mechanism for harvesting the algal cells 218 from thesupporting material 212. It will be appreciated that the drive motor 224can be associated with a plurality of mechanized harvesting units 222or, in an alternate embodiment, each mechanized harvesting unit can beassociated with an independent motor, gear, and/or drive shaft system.It may be efficient to operate one or more of the mechanized harvestingunits on the same schedule, but it may also be advantageous to operatesome or all of the mechanized harvesting units on different schedules.For example, in one embodiment, a mechanized harvesting unit exposed tonatural light can be associated with a light sensor (not shown) andcontroller (not shown) such that the rotation speed of the supportingmaterial is optimized relative to the available light. In such anexample, mechanized harvesting units in the same facility may havedifferent, or slightly different environmental conditions, whereoperating each mechanized harvesting unit independently maysubstantially optimize the overall system.

The mechanized harvesting unit 222 can have a generally wave-shapedconfiguration supported by the frame 223. It will be appreciated thatthe frame 223 can be constructed from any suitable material, such asmetal, and can have any suitable configuration in accordance withembodiments described herein. The supporting material 212 of themechanized harvesting unit can have a substantially wave-shapedconfiguration as best illustrated in FIG. 13. The supporting material212 can be a contiguous band of material and can be wound about the oneor a plurality of drive shafts 228 or rollers 229 such that any suitableconfiguration is created. It is contemplated that the supportingmaterial can be a long, contiguous band of material having multiplepeaks and valley, as illustrated in FIG. 12. As illustrated, a portionof the supporting material 212 can also pass along the bottom 250 of themechanized harvesting unit 222. It will be appreciated that a singlelong band and a plurality of bands having any suitable relationship orconfiguration are contemplated. In an example embodiment, the one or aplurality of drive shafts 228 or rollers 229 can be adjusted such thatdifferent configuration can be created using the same frame 223. Such aninterchangeable system may be beneficial in that certain configurationsmay be beneficial to particular species of algal cells. Aninterchangeable system may also allow for different environmentalconditions, uses, or use on a wide range of scales. Any other suitablecomponent, such as a plate 251 can be provided to secure components,such as the rollers 229, in a desired configuration.

Referring to FIGS. 14-16, shown is an alternate embodiment of arevolving algal biofilm photobioreactor (RAB) 300, in which algal cells318 can be attached to a solid surface of one or a plurality ofsupporting materials 312 that can be rotated between a nutrient-richliquid phase 315 and a CO2-rich gaseous phase 316 for alternativeabsorption of nutrients and carbon dioxide. The algal biomass can beharvested by scrapping the biomass from the attached surface with aharvesting mechanism (not shown) such as a squeegee, vacuum, reaper, orthe like. The photobioreactor 300 may require only a small amount ofwater for operation, relative to existing methods, where only the bottom350 (FIG. 15) of an algal growth unit or mechanized harvesting unit 322may be immersed in a contacting liquid 314. The photobioreactor 300 caninclude a frame 323, which can be positioned in a trough system 330containing contacting fluid 314. Example embodiments can include a largenumber of mechanized harvesting units such that the photobioreactor canbe scaled up to an industrial scale. For example, a single trough systemcould have 20, 50, 100, or more mechanized harvesting units orindependent supporting material units. In an example embodiment, the oneor a plurality of mechanized harvesting units 322 can be retrofittedonto existing raceway pond systems. Embodiments of the mechanizedharvesting units can be placed, for example, in any suitable fluidretaining location or device.

It will be appreciated that the trough system 330 is show by way ofexample only, where any suitable tubing, configuration, or constructionis contemplated. The trough system 330 can have a serpentineconfiguration such that the trough system 330 forms a substantiallyclosed circuit for fluid flow. The trough system 330 can have anysuitable shape, where the trough system 330 can have interchangeableparts such that different configurations can be created by a user. Thetrough system can include any suitable number of apertures 360 andclosed sections 362, where apertures 360 can be configured to accepteach of the one or a plurality of supporting materials 312. In oneembodiment, the apertures 360 can be associated with a closure when notin use. Alternatively, apertures 360 can be used in sunlight or welllighted areas to help facilitate algal growth in the contacting liquid314. The trough system 330 can be associated with a motor 338 andpaddlewheel 339 that can be configured to create a fluid dynamic orcurrent flow in the trough system 330. In one embodiment, one or aplurality of paddlewheels 339, or other actuators, can be positioned inthe apertures 360.

Embodiments of the photobioreactor 300 can include a drive motor 324 anda gear system 326 that can rotate one or a plurality of drive shafts328, where the one or a plurality of drive shafts 328 cancorrespondingly rotate the one or a plurality of supporting materials312, such as a flexible sheet material for growing algal cells 318. Thephotobioreactor 300 can include one or a plurality of rollers that cansupport and guide the one or a plurality of supporting materials 312 or,as illustrated in FIG. 15, the bottom of each of the one or a pluralityof supporting materials 312 can hang freely in a substantially verticalconfiguration. The one or a plurality of supporting materials 312 can berotated into contact with the contacting liquid 314, which can allow thealgal cells 318 to attach to the one or a plurality of supportingmaterials 312. The drive motor 324 can include a gear system 326 orpulley system that can drive the one or a plurality of drive shafts 328,where the one or a plurality of drive shafts 328 can rotate the one or aplurality of supporting materials 312 into and out of the contactingliquid 314. Embodiments can also include a trough system 330, mister,water dripper, or any other suitable component or mechanism that cankeep algae, which can be attached to the one or a plurality ofsupporting materials 312, moist. Embodiments can include any suitablescraping system, vacuum system or mechanism for harvesting the algalcells 318 from the one or a plurality of supporting materials 312. Itwill be appreciated that the drive motor 324 can be associated with aplurality of mechanized harvesting units 322 or one or a plurality ofsupporting materials 312. In an alternate embodiment, each of the one ora plurality of supporting materials 312 can be associated with anindependent motor, gear, and/or drive shaft system (not shown). It maybe efficient to operate one or more of the one or a plurality ofsupporting materials 312 on the same schedule, but it may also beadvantageous to operate some or all of the one or a plurality ofsupporting materials 312 on different schedules. For example, in oneembodiment, a supporting material exposed to natural light can beassociated with a light sensor (not shown) and controller (not shown)such that the rotation speed of the supporting material is optimizedrelative to the available light. In such an example, one or a pluralityof supporting materials in the same facility may have different, orslightly different environmental conditions, where operating each one ora plurality of supporting materials independently may substantiallyoptimize the overall system.

The mechanized harvesting unit 322 can have a generallyvertically-shaped configuration of one or a plurality of supportingmaterials 312 that can be supported by the frame 323. It will beappreciated that the frame 323 can be constructed from any suitablematerial, such as metal, and can have any suitable configuration inaccordance with embodiments described herein. Each of the one or aplurality of supporting materials 312 can be a contiguous band ofmaterial, strips, ropes, slats, ribbons, plates, scales, overlappingmaterial, or the like, and can be wound about the one or a plurality ofdrive shafts 328 or rollers (not shown) such that any suitableconfiguration can be created. It is contemplated that the supportingmaterial can be a long, contiguous band of material having multiplepeaks and valleys, or can be separate units as illustrated in FIG. 15.It will be appreciated that a single long band and a plurality of bandshaving any suitable relationship or configuration are contemplated.

Referring to FIG. 17, an example embodiment of an algal growth system ormechanized harvesting unit 422 is shown, in which algal cells 418 can beattached to a solid surface of a supporting material 412. Embodiments ofthe mechanized harvesting unit 422 can include a drive motor (notshown), and a gear system 426 that can rotate one or a plurality ofdrive shafts 428, where the one or a plurality of drive shafts 428 cancorrespondingly rotate the supporting material 412, such as a flexiblesheet material. Embodiments of the mechanized harvesting unit 422 caninclude a harvesting system 480 that can include any suitable manual orautomatic harvesting mechanism and/or a harvesting reservoir 482. Theharvesting system 480 can include a vacuum system 484 and a scraper 486for harvesting the algal cells 418 from the supporting material 412. Thescraper 486 can be coupled with a motor 488 and a pulley system oractuator 490 such that the scraper 486 can be selectively engaged withthe supporting material 412. The motor 488 can be associated with acontroller 492 such that the harvesting system 480 can be programmed toscrape, harvest, or perform any other suitable function automatically oron a predetermined schedule.

FIG. 20 depicts a flow chart illustrating one example of a method 1000that can be used for growing and/or harvesting algal cells using araceway, such as the raceway 130 shown in FIGS. 9 and 11. The method1000 can include Culturing Algal Inoculum 1002, which can includeculturing suspended algae in an open pond, raceway, or the like, untilthe algal cell density is between from about 0.05 g/L to about 1.0 g/L.It will be appreciated that any suitable density of any suitable algalcells is contemplated. The method 1000 can include Starting the RAB1004, which can include rotating or actuating the supporting material ofa photobioreactor, algal growth system, mechanized harvesting unit, orthe like, in accordance with versions described herein. The RAB or othersuitable system can be rotated, for example, at a speed ranging fromabout ¼ cm/sec to about 10 cm/sec. The RAB can be rotated at from about2 cm/sec to about 6 cm/sec. The RAB can be rotated at about 4 cm/sec.The RAB can be rotated or otherwise actuated at different speeds, whichcan be selectable, preprogrammed, or based on environmental conditions.Starting the RAB 1004 can include rotating the RAB system for anyduration of time such as from about 5 days to about 20 days, whereduration of operation can depend on the speed of the algal cellsattachment on the surface of the RAB materials.

The method 1000 can include Establishing Initial Biofilm 1006, which caninclude the growth of algal cells on the supporting material of an RABor photobioreactor. The initial biofilm can be deemed to be establishedwhen, for example, a threshold density of algal cells is determined.Such a threshold can be any suitable density and the density can bedetermined using any suitable system or method. The method 1000 caninclude Initial Harvesting 1008, which can include harvesting the algalbiomass from the supporting material of the RAB or photobioreactor.Initial Harvesting 1008 can be accomplished by scraping the algalbiofilm, vacuuming, pressurized air, or by any other suitable method.

The method 1000 can include Algae Regrowth 1010, where after harvesting,residual algal cells can remain on the supporting material surface andcan automatically serve as inoculum for a next cycle of growth orregrowth. Harvesting can be performed such that a sufficient density ofalgal cells can be left on the supporting material to facilitateregrowth. Algae Regrowth 1010 can include operating, actuating, orrotating the algal biofilm, RAB, or photobioreactor for any suitabletime period such as from about 3 days to about 8 days. The time foroperating the RAB can depend, for example, on the algal species, cultureconditions, rotating speed of the RAB system, the liquid fluid ratereservoir, or any other suitable factor. Method 1000 can includeRegrowth Harvesting 1012, which can include harvesting the algal biofilmthat has accumulated on the supporting material. The method 1000 caninclude repeating Algae Regrowth 1010 and Regrowth Harvesting 1012 foras many times as appropriate. The system can operate substantiallyindefinitely, or can be periodically interrupted for cleaning or forother reasons. The method 1000 can include Processing Algal Biomass1014, which can include processing the harvested algae by, for example,drying and extracting oil from the harvested algal cells. It will beappreciated that any suitable processing is contemplated.

FIG. 21 depicts a flow chart illustrating one example of a method 1100that can be used for growing and/or harvesting algal cells, such as witha photobioreactor 600 shown in FIG. 19, a trough, a partially enclosedfluid reservoir, or other suitable bioreactor. In such a system, it maybe beneficial to seed or otherwise provide algal cells grown at a firstlocation 602 (FIG. 19) and transport the algal cells via a channel 604(FIG. 19), or other suitable connection, to a second location 606 (FIG.19), such as to a photobioreactor provided in accordance with versionsdescribed herein. The first location can be fluidly coupled to thesecond location or, in an alternate embodiment, the first location canbe a portable bioreactor that can be selectively connected to the secondlocation as needed.

The method 1100 can include Culturing Algal Inoculum 1102, which caninclude culturing suspended algae in an open pond, portablephotobioreactor, or the like, at the first location until the algal celldensity is between, for example, from about 0.05 g/L to about 3.0 g/L.It will be appreciated that any suitable density of any suitable algalcells is contemplated, although in one embodiment the cell density canbe higher than in an open raceway system, where the reduction of lightin a trough system may benefit from a higher initial cell density. Themethod 1100 can include Circulating Algae 1103, which can includeproviding or otherwise delivering the algal cells from the firstlocation to the trough or partially enclosed system, which can includegenerating a fluid dynamic or flow such that algal cells from the firstgrowth region are transitioned to the trough in the second region. Themethod 1100 can include Starting the RAB 1104, which can includerotating or actuating the supporting material of a photobioreactor,algal growth system, mechanized harvesting unit, or the like, inaccordance with versions described herein. The RAB or other suitablesystem can be rotated, for example, at a speed ranging from about ¼cm/sec to about 10 cm/sec. The RAB can be rotated at from about 2 cm/secto about 6 cm/sec. The RAB can be rotated at about 4 cm/sec. The RAB canbe rotated or otherwise actuated at different speeds, which can beselectable, preprogrammed, or based on environmental conditions.Starting the RAB 1104 can include rotating the RAB system for anyduration of time such as from about 5 days to about 20 days, whereduration of operation can depend on the speed of the algal cellsattachment on the surface of the RAB materials.

The method 1100 can include Establishing Initial Biofilm 1106, which caninclude the growth of algal cells on the supporting material of an RABor photobioreactor. The initial biofilm can be deemed to be establishedwhen, for example, a threshold density of algal cells is determined.Such a threshold can be any suitable density and the density can bedetermined using any suitable system or method. The method 1000 caninclude Initial Harvesting 1108, which can include harvesting the algalbiomass from the supporting material of the RAB or photobioreactor.Initial Harvesting 1008 can be accomplished by scraping the algalbiofilm, vacuuming, pressurized air, or by any other suitable method.

The method 1100 can include Stopping Circulation 1109, which can includestopping delivery of algal cells from the first growth location to thesecond trough location, for example. In one embodiment, once the RAB isseeded with algal cells, the RAB may no longer need to be seeded orotherwise infused with additional algal cells for subsequent regrowthand harvesting steps. It will be appreciated that a feeder or seedingsystem for algal cells can be reattached or can be maintained throughoutif desirable. The method 1100 can include Algae Regrowth 1110, whereafter harvesting, residual algal cells can remain on the supportingmaterial surface and can automatically serve as inoculum for a nextcycle of growth or regrowth. Harvesting can be performed such that asufficient density of algal cells can be left on the supporting materialto facilitate regrowth. Algae Regrowth 1110 can include operating,actuating, or rotating the algal biofilm, RAB, or photobioreactor forany suitable time period such as from about 3 days to about 8 days. Thetime for operating the RAB can depend, for example, on the algalspecies, culture conditions, rotating speed of the RAB system, theliquid fluid rate of the reservoir, the type of reservoir, or any othersuitable factor. Method 1100 can include Regrowth Harvesting 1112, whichcan include harvesting the algal biofilm that has accumulated on thesupporting material. The method 1100 can include repeating AlgaeRegrowth 1110 and Regrowth Harvesting 1112 for as many times asappropriate. The system can operate substantially indefinitely, or canbe periodically interrupted for cleaning or for other reasons. Themethod 1100 can include Processing Algal Biomass 1114, which can includeprocessing the harvested algae by, for example, drying and extractingoil from the harvested algal cells. It will be appreciated that anysuitable processing is contemplated.

In various embodiments disclosed herein, a single component can bereplaced by multiple components and multiple components can be replacedby a single component to perform a given function or functions. Exceptwhere such substitution would not be operative, such substitution iswithin the intended scope of the embodiments.

Some of the figures can include a flow diagram. Although such figurescan include a particular logic flow, it can be appreciated that thelogic flow merely provides an exemplary implementation of the generalfunctionality. Further, the logic flow does not necessarily have to beexecuted in the order presented unless otherwise indicated. In addition,the logic flow can be implemented by a hardware element, a softwareelement executed by a computer, a firmware element embedded in hardware,or any combination thereof.

The foregoing description of embodiments and examples has been presentedfor purposes of illustration and description. It is not intended to beexhaustive or limiting to the forms described. Numerous modificationsare possible in light of the above teachings. Some of thosemodifications have been discussed, and others will be understood bythose skilled in the art. The embodiments were chosen and described inorder to best illustrate principles of various embodiments as are suitedto particular uses contemplated. The scope is, of course, not limited tothe examples set forth herein, but can be employed in any number ofapplications and equivalent devices by those of ordinary skill in theart. Rather it is hereby intended the scope of the invention to bedefined by the claims appended hereto.

We claim:
 1. An algal growth system comprising; a. a frame; b. a firstflexible sheet material mounted on a first frame in a first mountedgeometry, the first flexible sheet material having a substantiallyvertical orientation when mounted on the first frame such that theheight of the first mounted geometry is greater than the width of thefirst mounted geometry; c. a second flexible sheet material mounted on asecond frame in a second mounted geometry, the first flexible sheet andthe second flexible sheet material being noncontiguous, where the secondflexible sheet material has a substantially vertical orientation whenmounted on the second frame such that the height of the second mountedgeometry is greater than the width of the second mounted geometry; d. afirst drive shaft, the first drive shaft being coupled with the firstframe, wherein the first drive shaft supports and actuates the firstflexible sheet material, and a second drive shaft, the second driveshaft being coupled with the second frame, wherein the second driveshaft supports and actuates the second flexible sheet material; e. agear system, wherein the gear system is coupled with the first driveshaft and the second drive shaft such that the noncontiguous firstflexible sheet material and the second flexible sheet material areconcurrently actuated; f. a first roller coupled with the first frame toguide the first flexible sheet material, and a second roller coupledwith the second frame to guide the second flexible sheet material; g. adrive motor, the drive motor being coupled with the gear system, whereinthe drive motor actuates the gear system and the first drive shaft suchthat the first flexible sheet material is actuated and the second driveshaft such that the second flexible sheet material is actuatedconcurrently; h. a liquid phase and a gaseous phase, wherein the liquidphase comprises rotating the first flexible sheet material and thesecond flexible sheet material through a contacting liquid retainedwithin a fluid reservoir and the gaseous phase comprises rotating thefirst flexible sheet material and the second flexible sheet materialthrough a sunlight capture part wherein a majority of the first flexiblesheet material and the second flexible sheet material is positionedwithin the gaseous phase and a minority of the first flexible sheetmaterial and the second flexible sheet material is positioned within theliquid phase; i. a harvesting mechanism, wherein the harvestingmechanism is positioned entirely within a sunlight capture partassociated with the gaseous phase; and j. a raceway, at least a portionof the raceway being positioned beneath the frame, wherein the racewayat least partially defines the fluid reservoir.
 2. The algal growthsystem of claim 1, wherein the raceway is a trough.
 3. The algal growthsystem of claim 2, wherein the trough has a substantially serpentineconfiguration.
 4. The algal growth system of claim 1, further comprisingan automatic harvesting mechanism.
 5. The algal growth system of claim4, wherein the harvesting mechanism is a squeegee.
 6. The algal growthsystem of claim 1, wherein the first flexible sheet material and thesecond flexible sheet material are selected from the group consisting ofcheesecloth, fiberglass, porous PTFE coated fiberglass, chamois,vermiculite, microfiber, synthetic chamois, burlap, cotton duck, velvet,poly-lactic acid, abraised poly-lactic acid, vinyl laminated nylon,polyester, wool, acrylic, lanolin, woolen, cashmere, leather, silk,lyocell, hemp fabric, polyurethane, olefin fibre, polylactide, andcarbon fiber.
 7. The algal growth system of claim 1, wherein the algaeis selected from the group consisting of Nannochloropsis, Scenedesmus,Haematococcus, Botryococcus, Spirulina, Dunaliella, Arthrospira,Porphyridium, Phaeodactylum, Nitzschia, Crypthecodinium andSchizochytrium.
 8. The algal growth system of claim 1, wherein the drivemotor is associated with a programmable controller that is configured torotate the first flexible sheet material and the second flexible sheetmaterial on a predetermined schedule.
 9. The algal growth system ofclaim 1, wherein the first drive shaft is positioned directly above thefirst roller.
 10. The algal growth system of claim 1, wherein the firstflexible sheet material and the second flexible sheet material comprisea surface roughness, a hydrophobicity, and a positive surface charge.11. The algal growth system of claim 1, wherein the first flexible sheetmaterial and the second flexible sheet material comprise a plurality ofmaterials.
 12. The algal growth system of claim 1, wherein the racewayhas a plurality of apertures and closed sections.
 13. The algal growthsystem of claim 12, wherein the raceway includes a paddlewheel to createa flow pattern for the contacting liquid.
 14. The algal growth system ofclaim 12, wherein the raceway includes a pump to create a flow patternfor the contacting liquid.
 15. The algal growth system of claim 1,wherein the raceway is a serpentine trough.
 16. The algal growth systemof claim 15, wherein the serpentine trough includes a plurality ofapertures and a plurality of closed sections.
 17. The algal growthsystem of claim 13, wherein the raceway includes an actuator such that aflow pattern is generated within the raceway and wherein the firstflexible sheet material and the second flexible sheet material areoriented such that an axis of rotation of the first flexible sheetmaterial and the second flexible sheet material is parallel to the flowpattern generated within the raceway.
 18. The algal growth system ofclaim 17, wherein the actuator is driven by an actuator motor.